Southern tick-associated rash illness (STARI) is a newly-described Lyme disease-like infection reported from the southeastern and south central United States caused by Borrelia Ionestari. Our long-range goal is to understand the risk factors that conspire to allow maintenance of tick-borne bacterial pathogens in nature and transmission of these pathogens from the reservoir host-tick vector maintenance cycle to people. As our next objective in pursuit of this goal, we propose in this application to delineate the natural history of Borrelia Ionestari. Our central hypothesis is that Borrelia Ionestari is maintained in nature through a cycle involving white-tailed deer as primary reservoir host and lone star ticks as predominant vector, and that this system can be exploited to develop a geographic information system (GIS)-based model that predicts areas where humans are at greatest risk of infection. The rationale behind the proposed research is that field and experimental infection data collected to date indicate infection with Borrelia Ionestari is maintained in a deer-lone star tick reservoir system. To accomplish the objectives of this application, we will pursue four specific aims: (1) confirm that Borrelia Ionestari is maintained in a cycle involving white-tailed deer as reservoir host and lone star ticks as vector; (2) define the geographic distribution of Borrelia Ionestari in the United States using white-tailed deer as sentinels and lone star ticks as confirmatory indicators of the presence of infection in an area; (3) identify other potential wild vertebrate reservoir hosts and tick vectors that may be involved in the natural history of Borrelia Ionestari; and (4) evaluate rodents as a potential model for experimental infection with Borrelia Ionestari. At the completion of this research, we expect to have fully delineated the natural history of Borrelia Ionestari We also expect to have defined the geographic distribution of this pathogen in a manner that both examines the landscape epidemiology of this organism in detail and allows identification of areas where risk of human infection is high. Ultimately, the model of the natural history of Borrelia Ionestari gained from the proposed research will improve understanding of both STARI and Lyme borreliosis in the southern U.S., enhancing public health efforts in those areas where people are risk of infection; reduction in human disease from these pathogens should result. [unreadable] [unreadable] [unreadable] [unreadable]